1. Field of the Invention
The present invention relates in general to solar cells, and more particularly, to solar cells having improved front surface metallization.
2. Description of Related Art
Conventional solar cells consist of a semiconductor body having a P-type conductivity layer, an N-type conductivity layer, and N-P or P-N semiconductor junction between these layers, a front light-receiving major surface, and a back major surface, The layer adjacent the front surface is called the emitter, and the layer adjacent the back surface is called the base. When light energy impinges on the front light-receiving surface of the cell, electrons and corresponding holes are created in both the emitter and base. For the most part, because of the presence of the semiconductor junction, electrons will be directed toward on major surface of the cell and holes toward the other major surface, resulting in a photocurrent density. In a typeical P-N gallium arsenide semiconductor junction solar cell, holes move to the front light receiving surface of the cell and electrons toward the back surface. Electrical contacts are attached to the front and back surfaces of the gallium arsenide semiconductor body to collect the charge carriers. the electrons are collected by the back electrical contact and holes by the front electrical contact. the object is to collect as many electrons and holes as possible before they recombine, to attain the highest photo-current density possible.
A portion of the carriers directed toward the front surface, however, recombine under the front contact and thus do not contribute to the photo-current density. This is known in the art as the front surface recombination velocity. The front electrical contact of a gallium arsenide solar cell is one area where cell improvement has been sought by industry.